Split feed reforming and n-paraffin elimination from low boiling reformate

ABSTRACT

A processing combination is described for upgrading naphtha boiling range hydrocarbons by a combination of catalytic reforming and selective conversion of paraffinic components to enhance yield of aromatic hydrocarbons by contact with crystalline aluminosilicate catalysts having particular conversion characteristics.

D United States Patent 1 [111 3,770,614

Graven Nov. 6, 1973 4] SPLIT FEED REFORMING AND 3,395,094 7/1968 Weisz208/62 N I)ARAFFIN ELIMINATION FROM ow 3,432,425 3/1969 Bodkin et a1.208/80 3,114,696 12/1963 Weisz 208/66 BOILING REFORMATE 3,625,88012/1971 Hamner et a1. 208/111 [75] Inventor; Richard G. Graven, WegtmontNJ, 2,937,132 5/1960 Voorhies 208/64 [73] Assignee: Mobil OilCorporation, New York,

NY. Primary ExaminerHerbert Levine Attorney-Oswald G. Hayes, Andrew L.Gaboriault [22] Flled' 1971 and Carl D. Farnsworth [21] Appl. No.:106,837

52 us. Cl 208/62, 208/80, 208/92, I ABSTRACT 5 l t gg 5 A processingcombination is described for upgrading 66 naphtha boiling rangehydrocarbons by a combination I 1 0 can Q 2 of catalytic reforming andselective conversion of paraffinic components to enhance yield ofaromatic hydrocarbons by contact with crystalline aluminosilicate cat-[56] References C'ted alysts having particular conversioncharacteristics.

UNITED STATES PATENTS 3,236,903 2/1966 Milton .1 260/666 19 Claims, 2Drawing Figures lsom Prod.

TO Gasoline Blendlnq Light Nophtho from Hydrocrockmg H2 g Goslform as 51Run 32 Material 34 V 28 Reformore H Rich (305 Product 24 HGGVIGI' rhon HGasoline Rich 200--380F Reformole SPLIT FEED REFORMING AND N-PARAFFINELIMINATION FROM LOW BOILING REFORMATE BACKGROUND OF THE INVENTZON Theart of reforming naphtha hydrocarbons boiling in the gasoline boilingrange has been practiced in one form or another for many years. Overthese years the reforming process has developed to include regenerativeand semi-regenerative operations in combination with operations whereinthe total naphtha charge is passed sequentially through a plurality ofseparate catalyst beds or separate fractions thereof are passed throughone or more beds of reforming catalyst under condition of operatingtemperature, pressure and space velocity considered most suitable forachieving desired reforming reactions.

When hydrocarbons boiling in the gasoline boiling range are reformed inthe presence of a hydrogenationdehydrogenation catalyst, a number ofreactions take place which include dehydrogenation of naphthenes to formaromatics, dehydrocyclization of paraffins to form aromatics,isomerization reactions and hydrocracking reactions. When the reformingconditions are quite severe, coke formation'in the catalyst occurs withconsequent deactivation of the catalyst. Thus, it is quite apparent thatthe composition of the naphtha charge will necessarily influence theseverity of the reforming conditions employed to produce a desiredproduct. However, the reforming operations, as we known them today, havecertain built in limits because of reaction kinetics, catalystsavailable and equipment to perform the reforming operation. With theadvent of unleaded gasoline requirements a renewed interest has beengenerated to further adapt the reforming operation for the production ofhigh octane unleaded reformate gasoline product.

The treatment of a reformate with crystalline aluminosilicate zeolitesheretofore practiced has included both physical treatments such asselective adsorption, as well as chemical treatments such as selectiveconversion thereof.

Although the prior art procedures for treatment of a reformate differed,nevertheless, they had one common characteristic in that substantiallyall involved the use of crystalline aluminosilicates having a pore sizeof about Angstrom units. Another way of saying the same thing is tostate that substantially all prior art procedures for upgradingreformates with zeolites were concerned with those zeolites which wouldadmit normal paraffins and exclude isoparaffins. This was not toosurprising since it was known in the prior art that the undesirablecomponents in a reformate generally speaking, were normal parafiinswhereas other components of a reformate, i.e., the aromatics andisocontacted with a 5 Angstrom unit aluminosilicate inv order toselectively sorb out the normal paraffins.

"US. Pat. No. 3,1 14,696 represented'a substantial improvement in theproblem of upgrading a reformate since it was directed towards theconcept of treating a reformate with a crystalline aluminosilicatehaving a pore size of 5 Angstroms under cracking conditions so as toselectively crack out the normal paraffins.

US. Pat. No. 3,395,094 represented a still further advance in theoverall problem of upgrading a reformate. This patent was directedtowards the concept of hydrocracking the normal paraffins out of areformate with a crystalline aluminosilicate having a pore size of about5 Angstrom units and having hydrogenation activity limited to theinternal pore structure thereof. This patent realized that not only wasit necessary to selectively crack out normal paraffins, but also topreserve the aromatic constituents of the feed while this operation wasbeing carried out.

The present invention is concerned with further improvements inthe-method of producing gasoline products of acceptable octane ratingeither with or without a lead additive (TEL) or substitutes therefor andthe combination of processing steps to accomplish this purpose.

SUMMARY OF THE INVENTION This invention relates to the catalyticupgrading of naphtha hydrocarbons boiling over the gasoline boilingrange to form higher octane gasoline product. By the present inventionselected fractions of naphtha hydrocarbons are subjected to selectedreforming conditions, the lower boiling fraction thereof being subjectedgenerally to more or less severe reforming conditions than a higherboiling fraction thereof and particular reformate fractions obtained bythe reforming operations are further upgraded to higher octane productby one of several different selective conversion operations forconversion of undesired low octane components.

To effect octane improvement of gasoline boiling range naphthahydrocarbons, the present invention contemplates fractionating, forexample, a straight run naphtha boiling over the entire gasoline boilingrange, such as one boiling in the range of C hydrocarbons up to about400F. so as to recover a C rich fraction separately from a light naphthafraction boiling in the range of C hydrocarbon up to about 200F. A heavynaphtha fraction boiling from about 200F. up to about 400F. isseparately recovered. It is to be understood that the 200F. cut pointabove recited may be varied considerably depending upon the chargenaphtha composition and products desired. Therefore a cut point as lowas about 158 or F. may be selected or as high as 240F. may be employed.The cut point selected may even be up as high as about 300. In anyevent, the products desired from the operation of the present inventionwill greatly influence the cut point selected. For the purpose of thisdiscussion a cut point of about 200F. or 240F. will be used since it isintended to concentrate substantially all C hydrocarbons and asubstantial portion, if not a major portion, of C hydrocarbons into thelight naphtha fraction. The light naphtha fraction thus recovered andboiling in the range of about C hydrocarbons to about 200F. or 240F. issubjected to reforming operating conditions designed to convertnaphthenes to aromatics and in some cases effect some isomerization ofthe hydrocarbon constituents employing one or more beds of suitablereforming catalyst maintained under particularly selected temperatureand pressure conditions. Generally, naphthene dehydrogenation will beaccomplished in large measure in a single catalyst bed but more than onecatalyst bed may be desirable and employed in the presence of an aluminacontaining reforming catalyst available and known in the prior art. lnthe event that some isomerization of n-paraffins is desired, this may beaccomplished in still another bed of catalyst with a suitable reformingcatalyst maintained under conditions particularly suited for thispurpose.

It is generally known that a light naphtha low in naphthenes and high inparaffins is most difficult to reform. Because of this difficulty, thislight naphtha material is very often left unreformed and is disposed ofby blending with the product of reformed heavy naphtha.

The present invention provides a combination of catalysts operationwhich makes the reforming of light naphtha much more efficient and thismakes it desirable to upgrade even light naphtha to a higher octaneblending stock. In addition to the above, low octane npentane inadmixture with isopentane or in the absence thereof as the case may be,can be upgradedin octane by charging to the latter stage or lightnaphtha upgrading stage of the process therein defined. Thus thecombination process of this invention is unique in efficiently upgradingthe octane of low octane constituents. The charging of light naphtha toa platinum catalyst reforming stage and the reformate therefrom to azeolite catalyst upgrading stage is fortuitous in that the ratio ofn-paraffins and singly branched paraffins is in near optimal ratio withthe quantity of aromatics necessary to give maximum product yield at adesired octane. For the same reason of optimum paraffins to aromaticsratio, a light reformate cut from a full boiling range reformate mayalso be charged to the zeolite upgrading stage. It is also fortuitousthat a high hydrocarbon partial pressure is desirable in the zeoliteupgrading stage and this is conveniently obtained by charging lowboiling, low octane paraffin rich mixtures to this stage. Neverthelessit is recognized that some hydrogen partial pressure is desirable tosuppress coking of the catalyst. Hydrogen is conveniently supplied bythe dehydrogenation of naphthenes in the light naphtha charge overplatinum reforming catalyst. If the feed is deficient in naphthenes itmay be desirable to furnish supplemental hydrogen rich gas from anoutside source for the purpose of maintaining a desired minimal hydrogenpartial pressure.

The reformate product obtained from reforming a light naphtha fractionor otherwise obtained from a full boiling range reformate product byfractionation and having an end boiling point of about 200F. in aspecific example is thereafter subjected to a catalytic operationparticularly selective for the conversion of low octane paraffins inthis reformate fraction to permit ultimate recovery thereof as lowerboiling paraffins (i.e., propane and butane) and as alkylated product ofaromatic constituents in the reformate. Thus the removal of paraffinsfrom naphtha boiling range material as provided in a reformate may beaccomplished by contacting reformate material with a catalyst selectivefor converting substantially only n-paraffin components therein to thesubstantial exclusion of branched chain and aromatic compounds to lowerboiling paraffinic components, such as is possible by contact with asmall pore, 4 to 6 Angstrom crystalline zeolite cracking and/orhydrocracking catalyst. On the other hand, the reformate may becontacted with a new family of catalysts herein referred to as ZSM-Stype catalyst which have been found to have the property of alkylatingalkyl constituents existing and formed in the reformate upon contacttherewith to aromatic nuclei of the reformate.

It will be recognized by those familiar with the industry that theproducts produced will be a function of demand and economic advantage tothe producer. Thus, in some refinery operations there will be a greaterdemand and economic advantage for propylene and butylene rather than thesaturated compound thereof and in some operations the demand for methaneor LPG gases will take precedence. On the other hand, when the primaryinterest resides in the preparation of gasoline of acceptable unleadedoctane rating, the formation of alkylated products and branched chaincompounds of suitable clear octane rating of at least 94 or 95 willeffect some control on the operation selected.

The high boiling naphtha fraction above identified and boiling in therange of from about F. to 240F. initially up to about 380 or 400F. endpoint is subjected to a separate multiple bed reforming operationmaintained under reforming conditions particularly selective to upgradethis naphtha fraction to a higher octane product of at least 90 researchmethod octane numbers unleaded. The reforming operation selected toupgrade the high boiling portion of the naphtha charge may be of theregenerative or semi-regenerative type. Thus reforming of this heavynaphtha fraction boiling in the range of from about 180F. and preferablyfrom 240F. up to about 380 or 400F. may be accomplished at a pressure inthe range of from about 50 psig up to about 400 or 500 psig in thepresence of a platinum type reforming catalyst wherein the aluminasupport may be eta, gamma or mixed eta-gamma alumina either alone or incombination with one or more promoters including halogen such aschlorine or fluorine or a metal promoter known in the prior art. on theother hand, the reforming catalyst may be molybdenum on alumina or oneof the known bimetallic reforming catalysts known in the art with orwithout a halogen promoter. It is also contemplated employing differentcatalyst compositions in the separate reforming catalyst beds which willbe most effective to carry out one or more of the several catalyticreactions comprising reforming reactions.

The temperature employed during catalytic reforming will be a functionof the type of operation employed as will be the space velocity.However, reforming temperatures are usually in the range of about 800F.up to about 1000F. or higher and the space velocity will be in the rangeof from about 0.1 v/v/hr up to about 3 or 5 v/v/hr. In general, themolar ratio of hydrogen to hydrocarbon charge will be from about 1 toabout 20 and preferably will be from about 4 to about 8 or 10.

The catalyst employed to reform the lower boiling fraction may also beof the platinum type described above and used alone or in combinationwith metal promoters or a bimetallic reforming catalyst dispersed in asupport material comprising primarily alumina of the eta, gamma or amixed eta-gamma alumina type of support may be employed. The reformingcatalysts may be promoted with known metal promoters used alone or incombination with a halogen promoter. On the other hand, the reformingcatalyst may use halogen alone as promoter of the platinum type orbimetallic reforming catalyst and such halogen promoted catalyst may beused in only the reactors downstream of the first reactor.Molybdenum-alumina reforming catalysts may also be employed in thisoperation.

The reformer effluent or reformate product obtained from the abovediscussed reforming operations may be separated to recover hydrogen richgasiform material from the reformate product or hydrogen rich gasiformmaterial may be recovered with a portion of the reformate productboiling below about 260F. but more usually boiling below 240F. Hydrogenrich gasiform material separated from the hydrocarbon products of theprocess may require separation of normally gaseous hy- Y drocarbons froma hydrogen rich gaseous stream before recycle to the reforming operationor the selective conversion steps herein defined.

It has been found that reformate product material obtained as hereindiscussed and boiling in the range of from about C hydrocarbons up toabout 220F. or 240F. may be provided with a further octane boost andperhaps a yield boost by a selective conversion of low octane paraffincomponents found therein. Thus, in one embodiment a C to 240F. fractionobtained, as above described, may be subjected to one of the types ofselective catalytic treatment described above or this fraction may becombined with a light naphtha product of hydrocracking and/or a C normalparaffin rich fraction and thereafter subject to further conversiontreatment as herein defined. On the other hand, only the C paraffins maybe added to the light reformate before contact with the conversioncatalyst herein defined. In any event, it is important that theselective catalytic treatment be suitable for restructuring low octaneparaffin constituents found therein as by paraffin isomerization and byparaffin cracking which results in LPG, production and alkylation of lowboiling aromatics with fragments of the paraffin cracking reaction.

In yet another embodiment it is contemplated passing the total naphthacharge boiling up to about 380F. or

400F. through a platinum catalyst reforming operation and passing areformate product thereof boiling up to about 240F. either before orafter removal of hydrogen rich gaseous material therefrom in contactwith one of the shape selective conversion catalysts herein identifiedto effect the desired conversion of nparaffins and upgrading of thereformate material. On the other hand, the total reformate product ofthe reforming process may be passed over the selective conversioncatalyst for upgrading as herein defined, care being taken to controlthe hydrogen partial pressure within desired limits as well as thehydrocarbon to hy drogen ratio.

' In the processing combination of the present invention, it iscontemplated employing a charge naphtha comprising C hydrocarbons, whichC hydrocarbons will be initially separated from C and higher boilingmaterial by fractionation. It is also contemplated that some Chydrocarbons will be formed in the separate reforming operationsdiscussed. Therefore the processing combination of this invention willcontain means in some arrangements for separating and recovering Chydrocarbons from higher boiling hydrocarbons and these separatedhydrocarbons will be subjected to further treatment as by isomerizationor selective zeolite catalysis, as herein discussed.

For example, in the processing combination of this invention it iscontemplated separating the effluent obtained by reforming a naphthacharge boiling from about C hydrocarbons up to about 380F. at about its240 or 260F. cut point to obtain a heavy reformate product fractionseparately from reformer effluent material boiling below about 240 or260F. and containing hydrogen which material is thereafter processedover the selective conversion catalysts herein-defined to obtain adesired selective conversion of n-paraffins and improved octane ratingof the low boiling reformate material. Hydrogen may be separated fromthe product of the selective conversion step for recycle to thereforming operation or the selective conversion operation.

The separate reformate product streams obtained as hereinbeforediscussed and liquid products of the selective catalysis conversion canbe made to serve a multipurpose use as by blending. However, since theprimary purpose of the present invention is to prepare gasoline boilingrange materials having an acceptable octane rating which is free orsubstantially free of lead additive, blending of the various octaneproducts produced by the process will be particularly practiced toproduce a relatively low octane and a high octane gasoline product freeof lead. Particular blending techniques and compositions will generallybe within the discretion of the refiner to produce a desired productslate and may be varied considerably within relatively wide limitsdepending upon the product composition and/or slate desired. It iscontemplated employing the processing combination of the presentinvention to produce a product having a clear unleaded octane rating inthe range of to about 96 or 98 as well as a high octane gasoline producthaving an octane rating up to about 104 or 106 clear octane rating. I

Itis further contemplated that the upgrading reformate reactionsutilized to effect catalytic cracking of n-parafiins under selectiveconditions with a crystalline zeolite or crystalline aluminosilicatecatalyst will be carried out by contacting selected refonnate productfractions with the catalyst employing temperatures in the range of 700F.up to about l000 or 1 F. under essentially atmospheric or relativelyhigh pressure conditions up to about 1000 psig. Generally, pressuresbelow about 500 or 350 psig will be employed in the reforming step incombination with liquid hourly space velocities in the range of fromabout 0.1 up to about 10. Liquid hourly space velocities in the range offrom about 0.5 up to about 3.0 will be used for nickel erionite shapeselective conversion catalyst but above about 3 LHSV for the ZSM-S typeof conversion catalyst. The selective cracking catalyst may be employedin fixed bed, moving bed or fluid bed operations whichever offers thegreatest advantage. Generally, two parallel arranged fixed catalyst bedswhich will permit one catalyst bed to be regenerated as required duringonstream hydrocarbon conversion in the other bed of catalyst will be anacceptable arrangement. 7

Asmentioned above, the reformate materials may be subjected in oneembodiment to a selective hydrocracking operation to form saturatedproducts suitable as LPG products. In this selective hydrocrackingoperation the crystalline aluminosilicate cracking component generallyhas a pore size less than about 6 Angstroms and is associated with ahydrogenation component in such a manner that cracked paraffins free ofolefins will be formed under selected operating conditions most suitablefor that purpose. Thus the hydrogenation component may be locatedsubstantially internally, externally, or both internally and externallyto the zeolite pore structure of an erionite type of crystallinealuminosilicate and having a pore size in the range of from 4-6Angstroms.

The characteristics of crystalline aluminosilicates having a pore sizein the range of 4-6 Angstroms and their method of preparation has beenthe subject of several patents known in the prior art. In addition, thepreparation of zeolite cracking catalyst associated with a hydrogenationcomponent and suitable for the purpose of this invention has also beenthe subject of prior patent disclosure. Patents which may be referred tofor the above purpose include U.S. Pat. Nos. 3,114,696 and 3,395,094.

On the other hand, the ZSM-S type of conversion catalyst hereindiscussed is a crystalline aluminosilicate zeolite generally free of ahydrogenation component and provided with unusual catalytic properties.That is, the ZSM-S type of catalyst operation herein discussed isparticularly effective for treating reformate boiling in the range of Chydrocarbons up to about 220 or 240F. by virtue of the face that it willeffect cracking of the paraffin and alkylation of the product ofparaffin cracking to monocyclic aromatic compounds thereby increasingthe yield as well as the molecular weight of desired gasoline boilingrange material.

The ZSM-S type catalysts used in the novel process combination of thisinvention will allow entry into their internal pore structure normalaliphatic compounds and slightly branched aliphatic compounds,particularly monomethyl substituted compounds, yet substantially excludeall compounds containing at least a quaternary carbon atom or having amolecular dimension equal to or substantially greater than a quaternarycarbon atom. Additionally, aromatic compounds having side chains similarto the normal aliphatic compounds and slightly branched aliphaticcompounds above described could have said side chains enter the internalpore structure of the instant catalysts. Thus, if one were to measurethe selectivity of the ZSM-S type materials employed in the process ofthis invention, i.e., the ability to selectively sorb hexane from amixture of the same with isohexane, these catalysts would have to bestated as being non-shape selective. It should be immediately apparent,however, that the term selectivity has a far greater significance thanmerely the ability to preferentially distinguish between normalparaffins and iso-parafiins. Selectivity on shape is theoreticallypossible at any shape or size although, quite obviously, suchselectivity might not result in an advantageous catalyst for any and allhydrocarbon conversion processes.

While not wishing to be bound by any theory of operation, nevertheless,it appears that the crystalline zeolitic materials of the ZSM-S typeemployed in the instant invention cannot be characterized alone merelyby the recitation of a pore size or a range of pore sizes since it isalso known to have a relatively high silicato alumina ratio generallyabove 30 and often in excess of 60 to 1. It appears also that the poreopenings of these ZSM-S type zeolites are not approximately circular innature, as is more usually the case in many heretofore employedzeolites, but are more appropriately considered as approximatelyuniformly ellipitical in nature. Thus, the pore openings of the ZSM-Stype of zeolitic materials have both a major and a minor axes, and theunusual and novel molecular sieving effects appear to be achieved bythis ellipitical shape. It appears further that the minor axis of theelliptical pores in the zeolites apparently have an effective size ofabout 5.5 Angstrom units. The major axis appears to be somewhere between6 and about 9 Angstrom units. The unique molecular sieving action ofthese materials is presumably due to the presence of these approximatelyelliptically shaped windows controlling access to the internalcrystalline pore structure. In any event, irrespective of a particularmolecular dimension or of the pore sizes of the ZSM-S type catalyst thesimple fact remains that outstanding results have been obtained when ahydrocarbon mixture of normal paraffms and aromatics such as provided ina low boiling reformate or portions of a light reformate effluent isconverted over a ZSM-S type catalyst. It is to be noted that the wordconverted is being employed rather than merely stating that thereformate is cracked over a ZSM-S type catalyst for the very simplereason that the reaction mechanisms which are involved, althoughinclusive of cracking of normal paraffins, are far broader than thatspecific reaction. In fact, a novel contribution of the ZSM-S typecatalyst involves an entirely different chemistry than the chemistrywhich is identified as taking place in the heretofore practiced shapeselective cracking over an erionite type of zeolite having a pore sizeof about 5 Angstrom units, i.e., a process such as that described in theaforementioned U.S. Pat. No. 3,395,094. While not wishing to be bound byany theory of operation, nevertheless,

it appears that the novel contribution involves substantially more thanthe mere removal of normal paraffms by the selective cracking thereof togaseous products. Although the cracking of normal paraffins does,indeed, occur, there is also occurring a simultaneous alkylation of thecracked components with at least a portion of the aromatic in thereformate feed thereby resulting in an improved yield and highermolecular weight alkylated aromatic products in the absence ofsignificant amounts of produce LPG type of products.

It is contemplated, therefore, in one embodiment of this invention ofadding to an aromatic rich fraction, a highly paraffinic fraction or a Cstraight run gasoline fraction to, for example, a reformate material orselected portions thereof prior to its being converted over a ZSM-S typecatalyst. It has been found that a process of this type results inenhanced alkylation of particularly monocyclic aromatic components inthe feed thereby resultingin a much more valuable product provided aproper balance is maintained between the paraffin and aromaticcomponents coming in contact with the catalyst.

In its broadest form, it is clearly apparent that the present inventionrelates to the processing arrangement and combination of steps whichwill be effective for upgrading paraffin cyclic hydrocarbon mixtures andparticularly naphtha boiling range hydrocarbons comprising reforrnatesand/or selected portions of reformer effluents such as that boilingbelow about 260F. and more usually below about 240F. Thus upgrading ofthe hydrocarbon mixture to obtain improvement in at least its octanerating is accomplished by contact with a reforming catalyst and aselective conversion catalyst as typified by nickel erionite type ofcatalyst and the ZSM-S type of catalyst herein discussed.

The conversion of reformate materials comprising paraffins and aromaticcompounds may take place with or without the presence of hydrogen or ahydrogenation component in the selective catalyst composition. However,advantages in product obtained and catalyst on-stream life are realizedwith different degrees of magnitude depending on catalyst employed whenthe amount of hydrogen in the charge contacting the conversion catalystis present in carefully selected amounts. Thus it has been observed thattoo high a hydrogen partial pressure will undesirably influence thereaction mechanism of the ZSM-S type catalyst to the point that theadvantages attributed to this catalyst through alkylation are notrealized. This has also been found to be true when there is an improperratio between the normal paraffin and aromatics constituents in thecharge and particularly the monocyclic aromatics in the charge. Amaximum upgrading of the hydrocarbon charge through conversion over thenickel erionite type of catalyst does not rely upon the relationship ofthe paraffin-aromatic ratio but the catalyst life is considerablyinfluenced by the hydrogen partial pressure and temperature operatingconditions. Thus, when the ZSM-S type of catalyst is employeddown-stream of the reforming step, as provided in one embodiment of thepresent invention, it is believed that the alkylation effect or functionattributed to the catalyst is due to the initial formation of acarbonium ion upon cracking of the normal paraffin constituents in thefeed and the thus formed carbonium ion thereafter reacts with monocyclicaromatics to form alkylated aromatics. It has been found that in thisZSM-S conversion system, the hydrogen partial pressure can be used toinfluence cyclization of paraffins as distinguished from alkylation ofmonocyclic arrnoatics. On the other hand, it has been found that animproper hydrocarbon to hydrogen ratio will reduce the formation of thecarbonium ion and this effect will be further enhanced when the catalystis provided with hydrogenation activity. Thus during reactions with the'ZSM-S' type of catalyst it is particularly important to maintain properratio between paraffin and monocyclic aromatic components free of alkylradicals in the charge as well as the hydrogen partial pressuresubjectedto the reaction mechanisms of this catalyst in order 'to reapthe optimum conversion of the paraffins and alkylation thereof with thearomatics. Thus inthe processing embodiment it is contemplatedadding'anexc'ess of normal paraffins to the charge passed in contactwith the ZSM-S type of catalyst and such excess of normal paraffins willact to provide the desired balance between paraffin-aromaticconstituents as well as influence a reduction in the hydrogen partialpressure in the operation. In view of the above, it is evident,therefore, that separation of hydrogen rich gasiform material fromthereformate product may be accomplished before" or after passing theselected reformate product fraction boiling below about 240F. in contactwith the ZSM'-5 and nickel erionite type catalyst herein discussed.

In view of the above it is clear that the selectivity of the ZSM-S typecatalyst for effecting particularly alkylation of aromatics isinfluenced considerably by the operating conditions includingtemperature, pressure, space velocity in conjunction with the abovediscussed restrictions with respect to hydrogen partial pressure andhydrocarbon to hydrogen ratio.

Examples of zeolitic materials or crystalline zeolites which have beenfound operable as hereindefined are ZSM-S type catalyst compositionsdisclosed and claimed in copending application Ser. No. 865,472 filedOct. 10, 1969 now US. Pat. No. 3,702,886 as well as ZSM-8 crystallinezeolite compositions disclosed and claimed in copending application Ser.No. 865,418 filed Oct. 10, 1969 now abandoned. The family of ZSM-5catalyst compositions has the characteristic X-ray diffraction patternset forth in Table l, hereinbelow. ZSM-S compositions can also beidentified, in terms of mole ratios of oxides, as follows:

0.9 i 0.2 M ,,,O W 0 5-100 YO 2 H O wherein M is a cation, n is thevalence of said cation, W is selected'from the group consisting ofaluminum and gallium, Y is selected from the group consisting of siliconand germanium, and z is from 0 to 40. In a pre# ferred synthesized form,the zeolite has a formula, in terms of mole ratios of oxides, asfollows:

0.9 i 0.2 M O i A1 0 5-100 SiO z H 0 TABLE 1 Interplanar Spacing d(A)Relative Intensity 11.1 i 0.2 10.0 t 0.2 7.4 i 0.15 7.1 t 0.15 6.3 i 0.16.04 t 0.1 5.97 i 0.1 5.56 i 0.1 5.01 i 0.1

zssz gzszssszss These values as well as all other X-ray data weredetermined by standard techniques. The radiation was the K- alphadoublet of copper, and a scintillation counter spectrometer with a stripchart pen recorder was used. The peak heights, I, and the positions as afunction of two times theta, where theta is the Bragg angle, were readfrom the spectrometer chart. From these the relative intensities, 1/],where Us the intensity of the strongest line or peak, and d(obs.), theinterplanar spacing in A, corresponding to the recorded lines, werecalculated. In Table 1 the relative intensities are given in terms ofthe symbols S strong, M medium, Ms medium strong, MW medium weak and VSvery strong. It should be understood that this X-ray diffraction patternis characteristic of all the species of ZSM-5 compositions. Ion exchangeof the sodium ion with cations reveals substantially the same patternwith some minor shifts in interplanar spacing and variation in relativeintensity. Other minor variations can occur depending on the silicon toaluminum ratio of 'the particular sample, as well as if it has beensubjected to thermal treatment. Various cation exchanged forms of ZSM-5have been prepared. X-ray powder diffraction patterns of several ofthese forms are set forth below. The ZSM-S forms set forth below are allaluminosilicates.

TABLE 2 X-Ray Diffraction ZSM-S Powder in Cation Exchanged Forms dSpacings Observed As Made HCI NaCl CaCl ReCl AgNO, 11.15 11.16 11.1911.19 11.19 11.19 10.01 10.03 10.05 10.01 10.06 10.01 9.74 9.78 9.809.74 9.79 9.77 9.01 9.02 8.99 8.06 7.44 7.46 7.46 7.46 7.40 7.46 7.087.07 7.09 7.11 7.09 6.70 6.72 6.73 6.70 6.73 6.73 6.36 6.38 6.38 6.376.39 6.37 5.99 6.00 6.01 5.99 6.02 6.01 5.70 5.71 5.73 5.70 5.72 5.725.56 5.58 5.58 5.57 5.59 5.58 5.37 5.38 5.37 5.38 5.37 5.13 5.11 5.145.12 5.14 4.99 5.01 5.01 5.01 5.01 5.01

Zeolite ZSM-S can be suitably prepared by preparing a solutioncontaining tetrapropyl ammonium hydroxide, sodium oxide, an oxide ofaluminum or gallium, an oxide of silica and water and having acomposition, in terms of mole ratios of oxides, falling within thefollowing ranges:

TABLE 3 Particularly Broad Preferred Preferred OHlSiO, 0.071.0 0.1-0.80.2-0.75 R N-1-/(R N +NA 0.2-0.95 0.3-0.9 0.4-0.9 H O/OH 10-300 lO-30010-300 YO IW O 5-100 10-60 10-40 wherein R is propyl, W is aluminum andY is silicon maintaining the mixture until crystals of the zeolite areformed. Thereafter the crystals are separated from the liquid andrecovered. Typical reaction conditions consist of heating the foregoingreaction mixture to a temperature of from about C to 175C for a periodof time of from about six hours to 60 days. A more preferred temperaturerange is from about to 150C. with the amount of time at a temperature insuch range being from about 12 hours to 20 days.

The digestion of the gel particles is carried out until crystals form.The solid product is separated from the reaction medium, as by coolingthe whole to room temperature, filtering, and water washing.

ZSM-S is preferably formed as an aluminosilicate. The composition can beprepared utilizing materials which supply the appropriate oxide. Suchcompositions include for an aluminosilicate, sodium aluminate, alumina,sodium silicate, silica hydrosol, silica gel, silicic acid, sodiumhydroxide and tetrapropylammonium hydroxide. It will be understood thateach oxide component utilized in the reaction mixture for preparing amember of the ZSM-S family can be supplied by one or more initialreactants and they can be mixed together in any order. For example,sodium oxide can be supplied by an aqueous solution of sodium hydroxide,or by an aqueous solution of sodium silicate; tetrapropylammonium cationcan be supplied by the bromide salt. The reaction mixture can beprepared either batchwise or continuously. Crystal size andcrystallization time of the ZSM-S composition will vary with the natureof the reaction mixture employed. ZSM-8 can also be identified, in termsof mole ratios of oxides, as follows:

0.9 t 0.2 M2,,,O A1203 ssio z H2O wherein M is at least one cation, n isthe valence thereof and is from 0 to 40. In a preferred synthesizedform, the zeolite has a formula, in terms of mole ratios of oxides, asfollows:

0.9 i 0.2 M O A1 0 10-60 SiO 1 H 0 and M is selected from the groupconsisting of a mixture of alkali metal cations, especially sodium, andtetraethylammonia cations.

ZSM-8 possesses a definite distinguishing crystalline structure havingthe following X-ray diffraction pattern:

TABLE 4 A" 1/1, 1 dA 11.1 46 4 2.97 10.0 42' 3 2.94 9.7 2 2.86 9.0 6 12.78 7.42 10 4 2.73 7.06 7 1 2.68 6.69 5 3 2.61 6.35 12 1 2.57 6.04 6 12.55 5.97 12 1 2.51 5.69 9 6 2.49 5.56 13 1 2.45 5.36 3 2 2.47 5.12 4 32.39 5.01 7 1 2.35 4.60 7 1 2.32 4.45 3 1 2.28 4.35 7 1 2.23 4.25 18 12.20 4.07 20 1 2.17 4.00 10 1 2.12 3.85 100 1 2.11 3.32 57 1 2.08 3.75 12.06 3.71 6 2.01 3.64 26 6 1.99 3.59 2 2 1.95 3.47 6 2 1.91 3.43 '9 31.87 3.39 5 1 1.84 3.34 18 2 1.82 3.31 8

'Zeolite ZSM-8 can be suitably prepared by reacting a water solutioncontaining either tetraethylammonium hydroxide or tetraethylammoniumbromide together with the elements of sodium oxide, aluminum oxide, andan oxide of silica.

The operable relative proportions of the various ingredients have notbeen fully determined and it is to be immediately understood that notany and all proportions of reactants will operate to produce the desiredzeolite. In fact, completely different zeolites can be preparedutilizing the same starting materials depending upon their relativeconcentration and reaction conditions as is set forth in U.S. Pat. No.3,308,069. In general, however, it has been found that whentetraethylammonium hydroxide is employed, ZSM-8 can be prepared fromsaid hydroxide, sodium oxide, aluminum oxide, silica and water byreacting said materials in such proportions that the forming solutionhas a composition in terms of mole ratios of oxides falling within thefollowing range SiO /Al O from about 10 to about 200 Naoltetra'ethylammonium hydroxide from about 0.05 to 0.020

Tetraethylammonium hydroxide/SiO 4 from about 0.08 to 1.0

Id oltetraethylammonium hydroxide from about 80 to about 200 Thereafter,the crystals are separated from the liquid and recovered. Typicalreaction conditions consist of maintaining the foregoing reactionmixture at a temperature of from about 100C to 175C for a period of timeof from about six hours to 60 days. A more preferred temperature rangeis from about 150 to 175C with the amount of time at a temperature insuch range being from about 12 hours to 8 days.

, The ZSM-S type zeolites used in the instant invention usually have theoriginal cations associated therewith replaced by a wide variety ofother cations according to techniques well known in the art. Typicalreplacing cations would include hydrogen, ammonium and metal cationsincluding mixtures of the same. Of the replacing cations, particularreference is given to cations of hydrogen, ammonium, rare earth,magnesium, zinc, calcium, nickel, and mixtures thereof.

Typical ion exchange techniques would be to contact the particularzeolite with a salt of the desired replacing cation or cations. Althougha wide variety of salts can be employed, particular preference is givento chlorides, nitrates and sulfates. I

Representative ion exchange techniques are disclosed in a wide varietyof patents including U.S. Pat. Nos. 3,140,249; 3,140,251; and 3,140,253.

Following contact with the salt solution of the desired replacingcation, the zeolites may be washed with water and dried at a temperatureranging from 150F to about 600F and thereafter heated in air or otherinert gas at temperatures ranging from about 500F to 1500 F for periodsof time ranging from 1 to 48 hours or more.

It is also possible to treat the zeolite with steam at elevatedtemperatures ranging from 800F to I600F and preferably I0O0F and 1500F,if such is desired. The treatment may be accomplished in atmospheresconsisting partially or entirely of steam. This treatment may beaccomplished within a commercial cracking unit, e.g., by gradualaddition of the unsteamed catalyst to the unit.

A similar treatment can be accomplished at lower temperatures andelevated pressures, e.g., 350-700F at 10 to about 200 atmospheres.

A preferred embodiment of this invention resides in the use of a porousmatrix together with the ZSM-5 type zeolite previously described. TheZSM-S type zeolite can be combined, dispersed or otherwise intimatelyadmixed with a porous matrix in such proportions that the resultingproduct contains from 1 percent to percent by weight, and preferablyfrom 10 to 50 percent by weight, of the zeolite in the final composite.

The term porous matrix includes inorganic compositions with which thealuminosilicates can be combined, dispersed or otherwise intimatelyadmixed wherein the matrix may be active or inactive. It is to beunderstood that the proosity of the compositions employed as a matrixcan either be inherent in the particular material or it can beintroduced by mechanical or chemical means. Representative matriceswhich can be employed include metals and alloys thereof, sintered metalsand sintered glass, asbestos, silicon carbide aggregates, pumice,firebrick, diatomaceous earths, and inorganic oxides. Inorganiccompositions especially those of a siliceous nature are preferred. Ofthese matrices, inorganic oxides such as clay, chemically treated clay,silica, silica-alumina, etc., are particularly preferred because oftheir superior porosity, attrition resistance, and stability.

The compositing of the aluminosilicate with an inorganic oxide can beachieved by several methods wherein the alumino-silicates are reduced toa particle size less than 40 microns, preferably less than 10 microns,and intimately admixed with an inorganic oxide while the latter is in'ahydrous state such as in the form of hydrosol, hydrogel, wet gelatinousprecipitate, or in a dried state, or a mixture thereof. Thus, finelydivided aluminosilicates can be mixed directly with a siliceous gelformed by hydrolyzing a basic solution of alkali metal silicate with anacid such as hydrochloric, sulfuric, acetic, etc. The mixing of thethree components can be accomplished in any desired manner, such as in aball mill or other types of mills. The aluminosilicates also may bedispersed in a hydrosol obtained by reacting an alkali metal silicatewith an acid or alkaline coagulant. The hydrosol is then permitted toset in mass to a hydrogel which is thereafter dried and broken intopieces of desired shape or dried by conventional spray drying techniquesor dispersed through a nozzle into a bath of oil or otherwater-immiscible suspending medium to obtain speroidally shaped beadparticles of catalyst such as described in US. Pat. No. 2,384,946. Thealuminosilicate siliceous gel thus obtained is washed free of solublesalts and thereafter dried and/or calcined as desired.

In a like manner, the aluminosilicates may be incorporated with analuminiferous oxide. Such gels and hydrous oxides are well known in theart and may be prepared, for example, by adding ammonium hydroxide,ammonium carbonate, etc., to a salt of aluminum, such aluminum chloride,aluminum sulfate, aluminum nitrate, etc., in an amount sufficient toform aluminum hydroxide which, upon drying, is converted to alumina. Thealuminosilicate may be incorporated with the aluminiferous oxide whilethe latter is in the form of hydrosol, hydrogel, or wet gelatinousprecipitate or hydrous oxide, or in the dried state.

The catalytically inorganic oxide matrix may also consist of a pluralgel comprising a predominant amount of silica with one or more metals oroxides thereof selected from Groups IB, II, III, IV, V, VI, VII, andVIII of the Periodic Table. Particular preference is given to pluralgels or silica with metal oxides of Groups IIA, III and lVa of thePeriodic Table, especially wherein the metal oxide is rare earth oxide,magnesia, alumina, zirconia, titania, beryllia, thoria, or combinationthereof. The preparation of plural gels is well known and generallyinvolves either separate precipitation or coprecipitation techniques, inwhich a suitable salt of the metal oxide is added to an alkali metalsilicate and an acid or base, as required, is added to precipitate thecorresponding oxide. The silica content of the siliceous gel matrixcontemplated herein is generally within the range of 55 to 100 weightpercent with the metal oxide content ranging from O to 45 percent.

The inorganic oxide may also consist of raw clay or a clay mineral whichhas been treated with an acid medium to render it active. Thealuminosilicate can be incorporated into the clay simply by blending thetwo and fashioning the mixture into desired shapes. Suitable claysinclude attapulgite, kaolin, seipiolite, polygarskite, kaolinite,halloysite, plastic ball clays, bentonite, montmorillonite, illite,chlorite, etc.

Other useful matrices include powders of refractory oxides, such asalumina, alpha alumina, etc., having very low internal pore volume.Preferably, these materials have substantially no inherent catalyticactivity of their own.

The catalyst product can be heated in steam or in other atmospheres,e.g., air, near the temperature contemplated for conversion but may beheated to operating temperatures initially during use in the conversionprocess. Generally, the catalyst is dried between 150F and 600F andthereafter may be calcined in air, steam, nitrogen, helium, flue gas orother gases not harmful to the catalyst product at temperatures rangingfrom about 500F to 1600F for periods of time ranging from 1 to 48 hoursor more. It is to be understood that the aluminosilicate can also becalcined prior to incorporation into the inorganic oxide gel. It is alsoto be understood that the aluminosilicate or aluminosilicates need notbe ion exchanged prior to incorporation in a matrix but can be sotreated during or after incorporation into the matrix.

As has previously been stated, it is also possible to have ahydrogenation/dehydrogenation component present in the catalystcomposition.

The amount of the hydrogenation/dehydrogenation component employed isnot narrowly critical and can range from about 0.01 to about 30 weightpercent based on the entire catalyst. A variety of hydrogenationcomponents may be combined with either the ZSM-5 type zeolite and/ormatrix in any feasible manner which affords intimate contact of thecomponents, employing well known techniques such as base exchange,impregnation, coprecipitation, cogellation, mechanical admixture of onecomponent with the other, and the like. The hydrogenation component caninclude metals, oxides, and sulfides of metals of the Periodic Tablewhich fall in Group VIB including chromium, molybdenum, tungsten and thelike; Group IIB including zinc cadmium; and Group VIII including cobalt,nickel, platinum, palladium, rhenium, rhodium and the like andcombinations of metals, sulfides and oxides of metals of Group VIB andVIII, such as nickel-tungsten-sulfide, cobalt oxide-molybdenum oxide andthe like.

The pre-treatment before use varies depending on the hydrogenationcomponent present. For example, with components such as nickel-tungstenand cobalt molybdenum, the catalyst is sulfur activated. But with metalslike platinum or palladium, a hydrogenation step is employed. Thesetechniques are well known in the art and are accomplished in aconventional manner.

Within the above description of the ZSM-S type zeolites which can beused alone or physically admixed in a porous matrix, it has been foundthat certain aluminosilicates provide superior results when employed inthe process of this invention.

First of all, it is preferred that there be a limited amount of alkalimetal cations associated with the aluminosilicates since the presence ofalkali metals tends to suppress or limit catalytic properties, theactivity of which as a general rule decreases with increasing content ofalkali metal cations. Therefore, it is preferred that thealuminosilicates contain no more than 0.25 equivalents per gram atom ofaluminum and more preferably no more than 0.15 equivalents per gram atomof aluminum of alkali metal cations.

With regard to the metal cations associated with the ZSM-S typealuminosilicate, the general order of preference is first cations oftrivalent metals, followed by cations of divalent metals, with the leastpreferred being cations of monovalent metals. Of the trivalent metalcations, the most preferred are rare earth metal cations, eitherindividually or as a mixture of rare earth metal cations.

However, it is particularly preferred to have at least some protons orproton precursors associated with the aluminosilicate via exchange withammonium compounds or acids.

Having thus provided a general discussion of the im-' proved method ofthis invention reference is now w had to the drawings by way of examplefor a more clear understanding of the processing embodiment of themethod of this invention.

FIG. I identifies one arrangement of split feed reforming in combinationwith selective upgrading of low octane reformate product materialembodying the concepts of this invention.

FIG. II identifies an arrangement of naphtha reforming in combinationwith a selective upgrading of the light reformate product to produce animproved low boiling reformate product material embodying the conceptsof this invention.

Referring now to FIG. I of the drawings, a naphtha fraction boiling inthe gasoline boiling range and comprising from about C hydrocarbons upto about 380F. or 400F. is passed by conduit 2 to separator tower 4. Intower 4 the naphtha charge is separated to recover a C rich fractionwithdrawn overhead by conduit'6 from a low boiling naphtha fractionboiling in the range of C hydrocarbons up to about 240F. withdrawn byconduit 8 and a high boiling naphtha fraction boiling above 240F.withdrawn by conduit 10. The C rich fraction may be passed toisomerization upgrading in zone 12 from which an acceptableisomerization produce is recovered by conduit 14. The product ofisomerization may be separated by one or more different methods toisolate products suitable for blending with the reformate gasolineproduct. One method for effecting the separation is to pass theisomerization product in contact with a small pore (46 Angstroms)crystalline aluminosilicate which will be selective for separatingnormal from isomerized hydrocarbon material. In any event, the materialsof acceptable octane rating recovered from the product of isomerizationmay be used for blending with and/or the production of reformatematerial.

The C -200F. naphtha fraction recovered as above described is passed byconduit 8 to reforming zone 16. Reforming zone 16 comprises one or morecatalytic reactors arranged in sequence containing a reforming catalystpreferably of the platinum type wherein naphthenes are converted toaromatics as the primary reaction. With more than one reactor insequence in the reforming operation, the operating conditions andcatalyst employed may be selected to perform isomerization of the lighthydrocarbons passed thereto in additionto the cyclizing reactionsdesired in the absence of significant hydrocracking. The reformateproduct obtained in zone 16 is passed by conduit 18 to a high pressureseparator such as separator 20 wherein a hydrogen richrecycle gas isseparated from light reformate product. Hydrogen rich recycle gas isrecovered from separator by conduit 22 for recycle to the reformingoperation or use in other refinery operations as discussed herein. Therecycle hydrogen rich gas may be treated as known in the prior art toremove undesired low boiling C, to C or C hydrocarbon constituentstherefrom. The liquid reformate is withdrawn by conduit 24 and passedthereafter to catalytic upgrading in zone 26. Catalytic upgrading zone26 is intended to include a plurality of operations depending on thecatalyst (CAS) crystalline aluminosilicate employed to effect selectiveupgrading of the hydrocarbon materials passed thereto. That is, ahydrocarbon material comprising normal and isoparaffin in combinationwith aromatics may be upgraded as by selective cracking of paraffins tothe substantial exclusion of aromatics and branched chain compounds. Onthe other hand, the hydrocarbon material may be subjected to contactwith the class of catalyst identified herein as ZSM-S type of catalysts.It will be recognized by those skilled in the art that the catalystselected for use in zone 26 will depend in part upon the product slatedesired for a particular refinery operation. Thus, where the productionof LPG gaseous product is of interest, this suggests the use of a smallpore zeolite catalyst of about 5 Angstroms for the reasons discussedherein. The products of catalytic upgrading obtained in zone 26 arepassed by conduit 28 to separator 30. In separator 30, normally gasiformmaterial is separated from liquid components and withdrawn by conduit 32for passage to other processing treatment as discussed herein. Anupgraded light reformate product is withdrawn by conduit 34 for passageto gasoline storage and/or blending with material boiling above orheavier than gasoline being withdrawn from the bottom of the tower.

The heavy naphtha fraction boiling up to about 380F. is passed toreforming zone 36. Reforming zone 36 comprises a multiple reactorreforming operation of the regenerative or semi-regenerative tyep knownin the art wherein the heavy naphtha is passed in contact with a type ofplatinum reforming catalyst, such as a bimetallic reforming catalyst,and considered suitable for effecting the reforming operation hereindesired at a temperature in the range of from about 700F. up to about1000F or higher, employing a pressure of from about 50 psig up toseveral atmospheres of pressure. Generally, the reforming pressure iskept reasonably low and usually is below about 400 psig. In reformingzone 36, C and higher boiling hydrocarbons are subjected toreactionleading to the formation of aromatic and branched chain hydrocarbons ofrelatively high octane rating. The reformate product of zone 36 iswithdrawn by conduit 38 and passed to separator 40 wherein hydrogen richrecycle gas may be separated from liquid reformate product and withdrawnby conduit 42. A portion of the hydrogen rich recycle gas withdrawn asby conduit 22 and 42 may be separately recovered for use elsewhere inthe process such as for pretreating the naphtha charge to remove sulfur,or it maybe used to partially supply'the hydrogen requirements of zone26 of FIG. 1. Under some circumstances, excess hydrogen in conduit 42may be used in reforming step 16. Thus, hydrogen produced in thereforming steps may be cascaded through the process in a manner mostefficient for its utilization in the processing combination. Forexample, some of the withdrawn hydrogen rich gas from either zone 20 or40 may be combined or used separately for cascade first through thereformate upgrade zone 26 from which it may be passed to the naphthapretreater zone for effecting desulfurization of the naphtha charge. Theliquid refortower 46. In separator tower 46, the liquid reformateproduct is separated under conditions to separate a low boiling portionof the reformate boiling in the range of from about C hydrocarbons up toabout 200F. and as high as 260F. but more usually not above about 240F.from a higher boiling reformate product fraction boiling up to about380F. from a product fraction boiling above 380F. withdrawn from thebottom of tower 46.

The reformate product fraction boiling from about 200F. up to about380F. is withdrawn from the lower portion of separator 46 by line 50having an initial boiling point which depends in large part upon theproduct slate demanded of the process. The low boiling portion of thereformate separated in tower 46, on the other hand, may be used as ablending component in the preparation of regular grade gasoline. It ispreferred, however, to subject this fraction to further treatment withone of the selective conversion catalysts herein described to effect theconversion of low octane normal paraffins found in the product asdescribed above. FIG. 1 shows passing this low boiling reformatefraction obtained from separator 46 by conduit 48 to zone 26 for thedesired selective catalytic treatment. It is to be understood, however,that selective treatment of this light reformate fraction may also beaccomplished in a zone separate from zone 26 employing the same or adifferent selective catalyst compositiion. In any event, the

light reformate product is upgraded by removing normal paraffin of lowoctane rating thereby improving the hydrogen purity of a gaseous streamseparated from the product thereof and the product of the selectivecatalytic treatment of improved octane rating is then employed as ablending component to produce desired oc-v tane gasoline product.

To the extent desired the processing arrangement of FIG. I may bemodified so that the zeolite treating step 26 is between reforming zone16 and separator 20 so that the total reformate will be passed incontact with the zeolite upgrading catalyst. Furthermore, the reformateproduct of zone 36 may be separated after removal of hydrogen rich gasestherefrom to recover a reformate material boiling below about 200F. fromhigher boiling reformate material and passing the reformate boilingbelow 200F. thus separated with the total reformate product from zone 16in contact with the zeolite upgrading catalyst. In this combination, itmay be desirable to add a paraffin rich stream such as pentanes to thereformate material being passed in contact with the zeolite upgradingcatalyst.

FIG. ll departs from FIG. I primarily in the concept that a full boilingrange naphtha boiling from about C or C hydrocarbons up to about 380F.is passed over a platinum reforming catalyst in a plurality of separatecatalyst beds maintained under reforming conditions selected todehydrogenate naphthenes to aromatics, cyclize and isomerize paraffinsand raise the octane rating of the charge naphtha to a considerablyhigher level. Reforming operations to accomplish the above are wellknown in the prior art as indicated hereinbefore. It is known, however,that the product effluent of reforming and known as reformate in theprior art contains some low boiling component primarily n-paraffinswhich are of a low octane rating. Furthermore, depending upon thecomposition of the naphtha charge and the severity of the reformingoperation, the hydrogen containing recycle gas or gasiform material willvary considerably in composition and thus hydrogen purity. Therefore theprocessing combination of FIG. II is intended to include an operationwhich will not only upgrade low boiling reformate material to a higherand more desirable octane product but considerable improvement in thepurity of the hydrogen rich recycle gas may also be achieved. Thereforein the processing combination of FIG. II, the full boiling range naphthaenters the process by conduit 60 for passage to a catalytic reformingcombination or zone identified as 62. In the catalytic reformingoperation anyone of the known prior art reforming catalyst may beemployed, it being preferred to employ platinum type reforming catalystsand/or bimetallic reforming catalysts developed in recent years. Thereforming operation may be regenera tive or semi-regenerative asdiscussed above and usually will comprise at least three separate bedsof catalyst in separate reaction zones maintained under reformingoperating conditions discussed above. The reformer effluent or reformateproduct is thereafter normally passed to a high pressure separator firstand then a low pressure separator to effect the removal of low boilingnormally gasiform material from a higher boiling normally liquidreformate product. Generally hydrogen rich gaseous material is recoveredfrom the high pressure separator for recycle to the reforming operationthereby minimizing compression costs of the process with respect to thishydrogen containing stream. In the arrangement of FIG. II, the reformereffluent is passed by conduit 64 to a separator 66 which may be a highpressure separator. In separator 66 hydrogen rich recycle gas isseparated and removed by conduit 68 for recycle to the reforming step 62by conduit 70. Liquid reformate material is withdrawn from separator 66by conduit 72 for passage to a separator or splitter tower 74. On theother hand, bypass conduit 76 containing valve 78 is provided forpassing hydrogen rich reformer effluent gases directly from thereforming separator zone 66 to conduit 80 connecting with converter 84.Splitter tower 74 is provided primarily for the purpose of separatingthe reformate or reformer effluent into a low boiling reformate fractionand a higher boiling reformate fraction. In this specific example theseparation is made primarily for the purpose of concentrating low octaneparaffin components of C and lower boiling hydrocarbons such as C andlower boiling constituents into a low boiling or light reformate productfrom a more desirable higher boiling reformate material. Thus a lightreformate comprising n-paraffins and aromatics with or without addedhydrogen rich gas is passed from the upper portion of splitter tower 74by conduit 80 to converter 84 with the heavy reformate being recoveredfrom the bottom portion of the tower by conduit 82. Under someconditions, material heavier than desired gasoline product may berecovered from the bottom of tower 74 for use as desired.

The light reformate material in conduit 80 and boiling, for example,below about 240F. is then passed in contact with one of the selectiveconversion catalysts herein defined to obtain for example a desiredconversion of paraffins in the light reformate and the concentration ofaromatics in a product fraction subsequently recovered. For example,when employing an erionite based conversion catalyst, normal paraffinsmost usually will be converted to desired gaseous components such asliquid propane gas. On the other hand, when employing a ZSM-S type ofcatalyst, an improvement in both hydrogen purity of gasiform materialrecovered therefrom and an improvement in the molecular weight and-yield of aromatic constituents can be realized under particularlyselected operating conditions as discussed herein. For example, whenemploying the ZSM-S type of conversion catalyst in zone 84 it may bedesirable to combine some straight run normal paraf- 21 fins such as Cparaffin with the charge stream passed thereto and introduced by conduit94 so as to maintain, for example, the partial pressure of hydrogenwithin desired limits or the paraffin to aromatic ratio as hereindiscussed so that upgrading of this stream can be realized inconjunction with obtaining an alkylation of aromatic constituents in thelight reformate feed. The product of the selective conversion operationin zone 84 is then passed by conduit 86 to separator 88. Separator 88 isprovidedprimarily for the purpose of separating normally gaseouscomponents such as hydrogen containing gaseous components from a higherboiling aromatic enriched product of the process. The aromatic enrichedproduct is recovered from zone 88 by conduit 90 for passage to suitablegasoline blending pool not shown. The hydrogen rich gaseous phase iswithdrawn by conduit 92 for recycle as shown.

Having thus provided a general description of the present invention andpresented specific examples in support thereof, it is to be understoodthat no undue restrictions are to be imposed by reasonthereof except asdefined by the following claims.

I claim: I l. A method for upgrading a naphtha boiling hydrocarbonfraction to useful products including gasoline which comprisesseparating said naphtha fraction to recover light naphtha fraction froma higher boiling naphtha fraction, separately reforming said light andhigher boiling naphtha fractions under conditions selected to producelow and higher boiling paraffin containing reformate fractions,separating hydrogen rich gaseous material separately from the lowboiling paraffin containing reformate fraction boiling below 260F andsaid higher boiling reformate fraction, further converting paraffins inthe low boiling reformate fraction boiling below about 260F by contactwith a crystalline aluminosilicate catalyst of the'ZSM-Stype selectivefor restructuring paraffins therein, and recovering an aromatic enrichedproduct from said crystalline aluminosilicate catalyst contact step. a

2. The method of claim 1 wherein the ratio of aromatic to paraffin inthe charge to the crystalline aluminosilicate catalyst contact step isadjusted toassure an excess of paraffin.

3. The method of claim 2 wherein the paraffin is npentane.

4. The method of claim 1 wherein the hydrogen partial pressure of thecharge to the crystalline aluminosilicate catalyst contact step iscontrolled to a level selected to influence the alkylation of crackedparafiin constituent with aromatics.

5. The method of claim 1 wherein the crystalline aluminosilicatecataylst contact stepis effected in the substantial absence of hydrogen.

6. The method of claim 1 wherein the pressure of the crystallinealuminosilicate contact step is selected from a pressure equal toorhigher than the pressure of one or both 'of the reforming steps.

7. The method of claim 1 wherein hydrogen rich gas 6 in the charge tothe crystalline aluminosilicate catalyst contact step is sufficient tosuppress coking of the cata- .lyst.

8. The method of claim 1' wherein a light naphtha product ofhydrocracking is combined with the light naphtha fraction passed toreforming.

9. The method of claim 1 wherein the total reformate product of the highboiling naphtha fraction separated from hydrogen rich gas is passed tosaid crystalline aluminosilicate catalyst contact step.

10. The me'thod'of claim 9 wherein a paraffin rich fraction is combinedwith the light reformatematerial passed to said crystallinealuminosilicate contact step.

11. The method of claim 1 wherein a relationship is maintained betweenparaffins, aromatics and hydrogen in the light reformate fraction whichwill optimize the alkylation reaction in the crystalline aluminosilicatecontact step.

12. The method of claim 11 wherein paraffin alkylation is enhanced bythe addition of monocyclic aro matics.

13. A method for upgrading naphtha boiling range hydrocarbons togasoline product of improved octane rating which comprises,

separating said naphtha boiling hydrocarbons into a light naphtha chargeand a heavier naphtha charge, separately reforming the light and heavynaphtha charges, separating a hydrogen rich gas stream from thereformate product of each of said naphtha reforming steps, recyclingseparated hydrogen rich gas to the reforming step from which obtained,further separating said reformate product of said heavy naphthareforming step into a light reformate fraction and a heavier reformatefraction, combining the thus separated light reformate fraction with thereformate product of said light naphtha charge separated from hydrogenrich gas, passing the combined light reformate material obtained asabove defined in contact with a ZSM-S type crystalline aluminosilicatecatalyst having the property for restructuring paraffins by cracking, byisomerizing parafiins, by alkylating cracked paraffin constituents witharomatics present in the charge and recovering a gasoline boilingmaterial from said crystalline aluminosilicate contact step reducedin-n-paraffin components but of improved octane rating.

14. The method of claim 13 wherein hydrogen rich gasesare separated fromthe product of said crystalline aluminosilicate catalyst contact stepand recycled to the light naphtha reforming step.

15. The method of claim 13 wherein the hydrogen pressure of thecrystalline aluminosilicate catalyst contact step is controlled to limitcoke deposition and the ratio between paraffins and aromatics in thecharge thereto is controlled to optimize aromatics production.

16. The method of claim 13 wherein paraffin restructuring of the lightreformate fraction is accomplished under conditions promoting alkylationof cracked paraffins with aromatics in the presence of said crystallinealuminosilicate catalyst havingsaid restructuring properties.

17. A method for upgrading a naphtha hydrocarbon feed fraction boilingin the range of C hydrocarbons up to about 400F. to useful productsincluding gasoline which comprises a. separating the naphtha feedfraction to recover a light naphtha boiling in the range of Chydrocarbons through substantially C, type hydrocarbons from a higherboiling naphtha fraction,

b. separately reforming said light naphtha fraction and said higherboiling naphtha fraction to reformate product fractions,

c. separately recovering hydrogen rich gases from each of said reformateproduct fractions for recycle to the reforming step from which it isderived,

d. further separating the reforming product of said higher boilingnaphtha fraction into a light reformate material and a heavier reformateproduct,

e. combining the thus obtained light reformate material with thereformate product of said light naphtha fraction separated from hydrogenrich gases and passing the combined light reformate material in contactwith a crystalline zeolite conversion catalyst of the ZSM- type havingactivity and selecmatics.

13233 5 UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION PatentNo. 2.770.61h Dated November 6, 197% Inventor(s) RICHARD G. GRAVEN It iscertified that error appears in the above-identified patent and thatsaid Letters Patent: are hereby corrected as shown below:

Column 1, line 30 "known" should be --know-- Column 7, 'line- 21 "face"should be --fact- Column 8, line 37 "produce" should be --produced--Column 9, line 30 "armoatics" should be --a romatics-- Column 10', line38 After "1;" insert --o.o8--

Column 11, line 5O Under column "CaCl insert -2.l7 Column 14, line I"reference" should be --preference Column 14,.- line L4 "proosit shouldbe '--.porosity-- Column 17, I line 23 "produce should be "product--Column l8 line 22 "tyep" should be --ty'pe-- Signed and sealed this 7thday I of May 19m.

(SEAL) Attest: I

EDWARD l' l .FLETCHER JR v C MAI- SHALL DANN Attesting Officer-Commissioner of Patents

2. The method of claim 1 wherein the ratio of aromatic to paraffin inthe charge to the crystalline aluminosilicate catalyst contact step isadjusted to assure an excess of paraffin.
 3. The method of claim 2wherein the paraffin is n-pentane.
 4. The method of claim 1 wherein thehydrogen partial pressure of the charge to the crystallinealuminosilicate catalyst contact step is controlled to a level selectedto influence the alkylation of cracked paraffin constituent witharomatics.
 5. The method of claim 1 wherein the crystallinealuminosilicate cataylst contact step is effected in the substantialabsence of hydrogen.
 6. The method of claim 1 wherein the pressure ofthe crystalline aluminosilicate contact step is selected from a pressureequal to or higher than the pressure of one or both of the reformingsteps.
 7. The method of claim 1 wherein hydrogen rich gas in the chargeto the crystalline aluminosilicate catalyst contact step is sufficientto suppress coking of the catalyst.
 8. The method of claim 1 wherein alight naphtha product of hydrocracking is combined with the lightnaphtha fraction passed to reforming.
 9. The method of claim 1 whereinthe total reformate product of the high boiling naphtha fractionseparated from hydrogen rich gas is passed to said crystallinealuminosilicate catalyst contact step.
 10. The method of claim 9 whereina paraffin rich fraction is combined with the light reformate materialpassed to said crystalline aluminosilicate contact step.
 11. The methodof claim 1 wherein a relationship is maintained between paraffins,aromatics and hydrogen in the light reformate fraction which willoptimize the alkylation reaction in the crystalline aluminosilicatecontact step.
 12. The method of claim 11 wherein paraffin alkylation isenhanced by the addition of monocyclic aromatics.
 13. A method forupgrading naphtha boiling range hydrocarbons to gasoline product ofimproved octane rating which comprises, separating said naphtha boilinghydrocarbons into a light naphtha charge and a heavier naphtha charge,separately reforming the light and heavy naphtha charges, separating ahydrogen rich gas stream from the reformate product of each of saidnaphtha reforming steps, recycling separated hydrogen rich gas to thereforming step from which obtained, further separating said reformateproduct of said heavy naphtha reforming step into a light reformatefraction and a heavier reformate fraction, combining the thus separatedlight reformate fraction with the reformate product of said lightnaphtha charge separated from hydrogen rich gas, passing the combinedlight reformate material obtained as above defined in contact with aZSM-5 type crystalline aluminosilicate catalyst having the property forrestructuring paraffins by cracking, by isomerizing paraffins, byalkylating cracked paraffin constituents with aromatics present in thecharge and recovering a gasoline boiling material from said crystallinealuminosilicate contact step reduced in n-paraffin components but ofimproved octane rating.
 14. The method of claim 13 wherein hydrogen richgases are separated from the product of said crystalline aluminosilicatecatalyst contact step and recycled to the light naphtha reforming step.15. The method of claim 13 wherein the hydrogen pressure of thecrystalline aluminosilicate catalyst contact step is controlled to limitcoke deposition and the ratio between paraffins and aromatics in thecharge thereto is controlled to optimize aromatics production.
 16. Themethod of claim 13 wherein paraffin restructuring of the light reformatefraction is accoMplished under conditions promoting alkylation ofcracked paraffins with aromatics in the presence of said crystallinealuminosilicate catalyst having said restructuring properties.
 17. Amethod for upgrading a naphtha hydrocarbon feed fraction boiling in therange of C5 hydrocarbons up to about 400* F. to useful productsincluding gasoline which comprises a. separating the naphtha feedfraction to recover a light naphtha boiling in the range of C6hydrocarbons through substantially C7 type hydrocarbons from a higherboiling naphtha fraction, b. separately reforming said light naphthafraction and said higher boiling naphtha fraction to reformate productfractions, c. separately recovering hydrogen rich gases from each ofsaid reformate product fractions for recycle to the reforming step fromwhich it is derived, d. further separating the reforming product of saidhigher boiling naphtha fraction into a light reformate material and aheavier reformate product, e. combining the thus obtained lightreformate material with the reformate product of said light naphthafraction separated from hydrogen rich gases and passing the combinedlight reformate material in contact with a crystalline zeoliteconversion catalyst of the ZSM-5 type having activity and selectivityfor converting particularly paraffin components to products within thegroup comprising gaseous olefins, LPG gaseous products and alkylaromatics.
 18. The method of claim 17 wherein the ZSM-5 type crystallinezeolite conversion catalyst is maintained under conditions forconverting substantially only normal paraffins in the reformate productto gaseous products rich in either olefins or LPG paraffins.
 19. Themethod of claim 17 wherein the ZSM-5 type crystalline zeolite conversioncatalyst is maintained under conditions to form cyclic products andalkyl aromatics.